The present invention relates to a multicolor fluorescence detection type electrophoretic analyzer, and particularly relates to a multicolor fluorescence detection type electrophoretic analyzer adapted to a DNA sequencer using a plurality of capillaries or a plurality of fine channels as separation media for analyzing biological samples such as DNA (deoxyribonucleic acid), etc.
DNA analyzing techniques based on electrophoresis, particularly DNA sequencers, have become popular. With the increase of the needs of DNA analysis, analyzing throughput has been required to be enhanced.
One method for enhancing analyzing throughput is integration of separation media for simultaneous analysis of a plurality of samples. One conventional technique is a DNA sequencer in which thin-layer gel formed between two flat glass plates is used as a separation medium. In the DNA sequencer, a large number of samples are subjected to electrophoresis so that the samples are arranged side by side between two flat glass plates from one side to the opposite side. Therefore, a sufficient distance is required to be taken between migration lanes so that adjacent samples are not mixed in the lanes. Accordingly, the density of integration of separation media is limited.
On the other hand, a DNA sequencer in which capillaries each having a fine inner diameter are disposed parallelly to each other so that different samples are subjected to electrophoresis in the capillaries respectively to thereby enhance the degree of integration has been proposed as another conventional technique for integrating separation media. In the proposed technique, because the sectional areas of the lanes are reduced compared with the DNA sequencer using flat glass plates, the current due to the electrophoresis is reduced so that the generation of Joule heat can be suppressed. Accordingly, a higher electrophoresis voltage than the conventional voltage can be applied so that the samples migrate at a high speed. Further, a method in which fine grooves as migration lanes are formed in a surface of a glass plate has been also discussed. The discussed method is effective for enhancing the degree of integration of migration lanes.
Further, integration of detection systems is required for enhancing the throughput of analyzing. That is, methods for measuring a plurality of migration lanes simultaneously and measuring a plurality of wavelengths corresponding to a plurality of fluorophores simultaneously have been described, for example, in U.S. Pat. No. 5,062,942, U.S. Pat. No. 5,162,654, JP-A-2-269937, JP-A-2-269936, JP-A-1-116441, JP-A-1-148946 and JP-B-7-95033. In each of those methods, a two-dimensional charge coupled device (CCD) is used so that detection wavelengths and images of migration lanes are evolved and focussed in two-dimensional directions on a detector surface so that one axis corresponds to the detection wavelengths and the other axis corresponds to the images.
Because the two-dimensional CCD evolves and focuses the plurality of detection wavelengths and the plurality of images (positional information) of migration lanes in two-dimensional directions respectively on the surface of the detector, analytically unnecessary information is measured by a large number of devices on the surface of the detector. Practically, unnecessary portions must be, however, removed by signal processing so that only useful portions are used selectively because necessary information concerning wavelengths and positions is present only in a slight portion. Because a large detector, however, has a large number of devices on its surface, both signal transferring and signal processing are so complex that a large time is generally required for the signal transferring and signal processing. Furthermore, the devices per se are so expensive that the cost of the devices inclusive of circuits for performing the signal transferring and signal processing at a high speed increases.
If linear array sensors can be used as detection devices in necessary positions, not only the system can be configured relatively inexpensively but also measurement can be performed in necessary portions limitedly. Accordingly, there is a possibility that data transferring and data processing are made speedily and simply.
Therefore, the present inventor has examined that a plurality of linear array sensors are disposed in a plane so as to be substantially equivalent to the two-dimensional sensor so that two-dimensionally evolved images are detected by such linear array sensors to thereby simplify signal processing. When the linear array sensors each having a light-receiving surface which per se is small in external size of about 30 mm.times.0.5 mm are mounted on a substrate, the external size is, however, enlarged to about 50 mm.times.50 mm. It is therefore difficult to realize the configuration in which the linear array sensors are disposed in a plane. Even in the case where images of the plurality of migration lanes are distributed into light paths by a polygonal prism, the distance between focussed spots is limited to a range of from about 5 mm to 8 mm at the maximum. This is because the detector has a large external size of about 50 mm.times.50 mm so that the distance between each migration lane and a corresponding lens of the detector must be taken large. Accordingly, the quantity of fluorescence taken in the detector through the lens among fluorescence radially diffused from the migration lanes is reduced so as to be inversely proportional to the square of the distance. Consequently, detecting sensitivity is reduced.
A DNA sequencer in which fluorescence from a plurality of migration lanes is detected simultaneously without use of any two-dimensional sensor is disclosed in U.S. Pat. No. 5,439,578. According to the U.S. Pat. No. 5,439,578, fluorescence emitted from a plurality of capillaries disposed parallelly to each other is introduced into optical fibers through condenser lenses and filters, and light is made incident from the optical fibers to photo detectors so as to be detected by the photo detectors.